The court has heard that cold case forensic evidence was found on Mr Dobson's jacket and cardigan, but the defence claims he never wore the jacket after it had been "ridiculed" and that the cardigan belonged to his father.

The allegation that fibres from Mr Lawrence's red shirt had landed on Mr Dobson's jacket during the attack was "unsubstantiated conjecture", said Mr Roberts.

It was much more likely that the police seized the clothing and put the items into their "leaky exhibit system", he said.

Mr Roberts said the fibres on the jacket could be traced back to when an accident and emergency nurse cut off Mr Lawrence's clothes, releasing a "shower" of material.

Prosecutors allege that a blood stain found on Mr Dobson's jacket was caused by Mr Lawrence's fresh blood, but Mr Roberts said it was "a creation of laboratory procedures".

The defence has argued an old dried blood flake got on the jacket via contamination and caused a spot when it was dissolved during tests for saliva.

'Shared hatred'

Earlier in the trial, the jurors were shown a police surveillance video showing racist rants by the two defendants and their friends.

Mr Roberts compared the video with the recent controversy over TV presenter Jeremy Clarkson calling for public sector workers who went on strike to be shot in front of their families.

Image caption
Mr Dobson's parents had told the court he was at home at the time

He said that neither Mr Clarkson nor his client had displayed murderous intent or meant their comments to be taken seriously.

Prosecutor Mark Ellison QC, who concluded the case against the two defendants on Wednesday morning, had said the video demonstrated a "shared hatred" of black people, a familiarity with knives and that they were "the sort of people expected to act how they acted when they came across two black people on that night".

He told jurors Mr Norris and Mr Dobson were "part of a likeminded group of white youths" on the night of the murder.

He said a series of forensic scientists had shown the only plausible explanation for fibres, blood and hair from Mr Lawrence being found on the defendants' clothes was their presence during the attack.

The jury was told that to convict Mr Dobson and Mr Norris they must be sure the forensic evidence against them had not been contaminated by mishandling over the years.

If they were sure there was no contamination, they must be certain the two men participated in the attack and that both of them knew there was intent to harm the teenager, said Mr Ellison.

The trial was adjourned to Thursday, when the jury will hear the defence case for Mr Norris.